The install file contains the parameters unique to the server, such as the account names and server name. The SET %SQLVERSION% statement causes this server to be built with SQL Server 2008 R2 and not with the default version of SQL Server used elsewhere.

2) When the install file is run, it runs the role file to pick up the standard role parameters. The role file then runs the environment default values file which in turn invokes FineBuild with the combined set of parameters and installs SQL 2008 R2.